Calcoolate

I wish the following conversion rate was correct. I could have replaced Bill Gates at the Forbes list(I bet that they will fix this soon. )

Colcoolate is a calculator and conversion application using AJAX. via Techcrunch I like their philosohpy too "Everything should be web based."

the way that they are doing the session history is very nice
The duo Itai Raz and Yoah Bar-David have another application called irows. Worth checking it out.